’98 BMW Z3M Coupe
Early 2018 we’ve got asked to rebuild this 1998 Z3M Coupe. It had been in storage for over 3,5 years and the owner wanted to wanted the have the S50 drivetrain in tip top condition before start to using it again. Together with the customer we made a list of “to-do’s” based on our recommendations, customer experience and the service history. Some highlight’s from the long task list included: Complete Vanos overhaul, Throttle body service and synchronization, injector service, new engine mounts, new clutch and flywheel, shifter mechanism rebuild, Vacuum system overhaul, new wishbones, and many more. Off course we also give the car a extensive wash and polish.
We’ve started with the collection of the car in Belgium.
Back in the workshop we first took our time to admire the car. In our opinion one of the most special BMW’s ever made.
Time to start the wrenching on the car. We begin with a compression test to see how the condition of the S50 is after 200.000 km.
The VANOS unit of the S54 is in principle the same as the more commonly known S54 vanos unit, but has a few differences, which gives a nice in-sight how the BMW engineer’s optimized the design of the S54 vanos unit from the S50 unit.
The condition of the vanos unit was very poor. We could easily rock the Camshaft, so the VANOS was definitively in need of a rebuild!
The vanos unit removed;
The vanos unit could definitely use a cleaning! The seals of the solenoids often break (like all other seals of this vanos) and starts to leak. The leaking seals are replaced by S62 trapezium shaped solenoid seals, which seal much better.
Meanwhile, to ITB’s are removed and ready to be cleaned and polished. There has a been a lot of dirt build up over de years, so a service is well worth the effort.
As the customer complained about a “loose” clutch pedal, we replaced the clutch pedal bushings with a bronze “upgraded” versions. A huge difference compared to the worn about plastic version.
Two O-Rings were completely gone. No wonder the VANOS didn’t work properly and was leaking…
We “opperate” the VANOS in order to properly clean them;
Before we could install the new seals, we conducted a lot of cleaning work. To illustrate the dramatic difference before and after, before and after;
Meanwhile, we proceeded with loosening the hubs so we could install stronger diaphragm springs (S62), quite a job with the S50 because the exhaust camshaft has to be completely removed in order to have enough room to remove the hub. The diaphragm springs were so weak that the splined shaft of the inlet camshaft could be pulled out by hand…
Intake hub can be removed with camshaft installed;
The axles of the splined shaft removed in order to be able to installed the new anti-rattle kit. This should be precisely shimmed out, which means a few loops of installing, measuring and disassembling again.
A few overview photo’s of the VANOS subcomponents;
Time to reassemble the VANOS. First we installed the hubs with the S62 springs;
Now that the timing is secured again, we are able to rotate the engine. A good moment to check the valve clearance, which didn’t require any adjustment;
While we’re add it, it is worth documenting which shims are used so a next “adjustment” can be done much quicker;
To be able to properly synchronize them, we designed our “sync tool” for the S50 as well and printed them on our 3D printer;
Next step is to conduct and injector check and service on our injector testbench. We check the injectors for leak, spray pattern and flow.
Beside the steps describes above, we also cleaned and replaced a large part of the vacuum system and crankcase ventilation system. Absolutely well worth it as many little hose we’re already leaking or almost leaking. It is not interesting to show all the hose, but a good example of the condition of the hoses;
We’re getting close to closing the engine again, so it is time to replace the engine oil. We fill the first liters will the engine is still open, so engine is already divided when the engine starts to rotate.
Offcourse we close the engine with a cleaned valve cover;
Next up was the exterior. Although the car looks already shine on the photos, in real life there was definitely improvement to be made;
The trained eye already noticed the Z3M had the wrong M-logo on the back. We replaced the newer (s54 logo) with the correct (s50) logo. Off course we took our time to place the logo on exactly the right position;
While we are at it, it is definitely worth replacing the shifter mechanism;
We began by drilling small holes at the end of all fractures. It is important to do this before removing the bodycoating, as the grinding marks might disguise the true beginning and ending of the crack. Once the hole was drilled, we carefully removed the paint/bodyspray;
Next step is to carefully “grind’ a groove in the crack, so it easy to make a good penetrated weld. We installed a long bolt in the hole, to check for alignment and adjust when required;
After welding and grinding, there is no sign of the crack to be seen anymore;
Meanwhile we bought a new transmission mount, with new mounting rubbers;
With the transmission done, we moved to the front of the car to replace the wishbones and rubbers. Most difficult part of this job was to get OEM wishbones, as there were in backorder at BMW and the dealer was not able to give a date when they would be available. We managed to purchase the LHS wishbone in Germany and the RHS in France;
The rubbers were still the original once from ’98;
While underneath the car, we conducted some standard service work like a brake fluid change, clutch fluid change, differential fluid change and repaired an steering fluid leak. The oil leaks from the engine and steering fluid covered the hole underside of the engine in a grease and dirt. With the leaks fixed, we cleaned all old debris off to make sure with a next service job a starting leak can easily be spotted and tracked down. An example of some cleaning;